Probes can be used to collect sample fluid streams from main fluid streams. For example, probes can be used to collect sample fluid streams from stack emissions, such as wet stack emissions. Wet stacks are stacks containing main flows of emissions that are saturated with water vapor and have liquid water droplets that can vary from micro droplets typical of fogs (micrometers in diameter) to macro droplets typical of rain (millimeters in diameter). These droplets can contain a large fraction of particulate matter (PM) and metals associated with health effects. It can be difficult to collect a representative sample of these droplets for analysis on a continuous basis. Currently, continuous emission monitor systems (CEMS) use large diameter probes to reduce deviations from isokinetic sampling, avoid heating sampling probes to minimize dried salt plugs, use steam and compressed air “blow back” to prevent probe build up and plugging, or other similar techniques to allow continuous operations.